docs: def _check_aligned_header(self, data_type, unit):
          """Check the header inputs whenever get_aligned_collection is called."""
          if data_type is not None:
              assert isinstance(data_type, DataTypeBase), \
                  'data_type must be a Ladybug DataType. Got {}'.format(type(data_type))
              if unit is None:
                  unit = data_type.units[0]
          else:
              data_type = self.header.data_type
              unit = unit or self.header.unit
          return Header(data_type, unit, self.header.analysis_period, self.header.metadata)